The molded plastic knobs of this invention are of the general type of friction fit knobs shown and described in U.S. Pat. No. 3,679,252 of Robert K. Howie, Jr.; U.S. Pat. No. 4,179,771 of Paul Rankins and Robert K. Howie, Jr.; U.S. Pat. No. 4,295,246 of Robert K. Howie, Jr.; and U.S. Pat. No. 4,441,230 of Robert K. Howie, Jr., all of which are assigned to the assignee of this application.
An object of this invention is a friction fit knob having force applying fingers which are resistant to creep during the long term application of force to the shaft.
Another object of this invention is a friction fit knob having force applying fingers positioned so that the insertion of the shaft into the socket compresses the fingers in a columnar direction.
Another object of this invention is a friction fit knob having force applying fingers which are positioned relative to each other such that the contact of the curved outer surface of the shaft with the fingertips when the shaft is inserted in the socket will both compress the fingers in an end-to-end direction and bend the fingers into contact with each other so that the load will be applied from one finger to another as in a bridge truss.
Another object of this invention is a friction fit knob having resilient fingers which extend generally tangentially to the shaft with ribs formed on each finger near its tip, the ribs being engaged by the curved outer surface of the shaft when the shaft is inserted in the socket to bend the curved fingers away from the shaft, with the amount of projection of the ribs toward the shaft determining the amount of bending of the fingers and thus the force applied by the fingers to the shaft.
Another object of this invention is a friction fit knob having tensioning fingers with a rib formed on each finger near its base. The rib is engaged by the shaft to create a line of interference between the shaft and the rib to provide a friction fit which does not require an undue amount of force to insert the shaft into the socket but resists pull-out of the shaft.
Another object of this invention is a friction fit knob having force applying fingers in which the tips of the fingers are notched for a prescribed depth at the entrance to the socket to facilitate the insertion of the shaft into the socket by virtually eliminating friction drag on the shaft during the piloting of the shaft into the socket.
Other objects may be found in the following specification, claims and drawings.